Still reeling from his breakup, Adam (Justin Long) is devastated when he learns that his ex, Allison (Cobie Smulders),is engaged. What's worse is he's invited to the wedding. Against the advice of his best friend Mark (John Cho), Adam decides to drive back home to San Francisco to attend the dreaded nuptials.

When Adam reluctantly arrives for the festivities, he must confront his unresolved feelings and an uncertain future in hopes of convincing himself and everyone else that he is truly happy Allison. There he discovers the comedy in romance, the tragedy of letting go and the hard truth about growing up.